Computer systems include numerous electrical components that draw electrical current to perform their intended functions. For example, a computer's microprocessor or central processing unit (“CPU”) requires electrical current to perform many functions such as controlling the overall operations of the computer system and performing various numerical calculations. Generally, any electrical device through which electrical current flows produces heat. The amount of heat any one device generates generally is a function of the amount of current flowing through the device.
Typically, an electrical device is designed to operate correctly within a predetermined temperature range. If the temperature exceeds the predetermined range (i.e., the device becomes too hot or too cold), the device may not function correctly, thereby potentially degrading the overall performance of the computer system. Thus, many computer systems include cooling systems to regulate the temperature of their electrical components. One type of cooling system is a forced air system that relies on one or more cooling fans to blow air over the electronic components in order to cool the components.
The cubic feet per minute (“CFM”) of air that can be moved across an electric device is an important factor in how much heat can be removed from the device. Thus, the capacity of a cooling fan is a critical factor in selecting an air mover for use in a cooling application. The CFM that a cooling fan can produce is governed by a number of factors including: the total area of the blades generating the airflow, the free area provided for airflow through the fan, the design of the blades, and the power generated by the electric motor.
Axial flow fans generally comprise a plurality of radial blades rotating within a housing. Increasing performance demands on axial flow fans have required that fans provide increased volumes of air while, at the same time, reducing the size of the fan. One solution to increasing fan performance is simply to increase the speed at which the fan rotates. Increasing fan speed can also be accompanied by increased acoustic emissions, increased vibration, and decreased component life. Therefore, as can be appreciated, there remains a need in the art for cooling fans that provide high volumes of airflow by designs and improvements that increase performance without necessitating an increase in the speed at which fan operates.